Squeezebottle dispensers having fluid-containing, flexible inner bags within them are common in the art. When a squeezebottle dispenser is squeezed, fluid is forced from the flexible inner bag through a discharge opening at the top of the dispenser. Valving in the dispenser enables air to be compressed within the squeezebottle during squeezing, but valving then allows air to vent into the bottle to replace the dispensed fluid after the squeezebottle is released. Repeated squeezing cycles cause the flexible inner bag to collapse around the fluid within the squeezebottle as the flexible inner bag empties.
A problem with such dispensers is that a flexible inner bag tends to collapse most quickly near its discharge opening. This is believed to be due to higher velocity fluid flow near the discharge opening causing lower static pressure there. Fluid flow may be choked off from the rest of the flexible inner bag if the flexible inner bag collapses prematurely near the discharge opening. To correct this problem, the manner in which the flexible inner bag can collapse is generally controlled. For example, a flexible inner bag may be designed to collapse radially about a perforated diptube connected to the discharge opening of the squeezebottle. In some circumstances, for example, when the fluid is highly viscous like toothpaste, diptubes generally provide too much resistance to fluid flow through them. For such fluids, which have viscosities great enough that they cannot flow under gravity, another collapse control approach is often used. That is, a flexible inner bag is affixed to the upper half of the inside of a squeezebottle so that the flexible inner bag can collapse by inverting axially toward the discharge opening. Flexible inner bag inversion offers minimum flow resistance.
For squeezebottle dispensers having flexible inner bags which invert toward the discharge opening, there is often a construction problem involved with inserting and affixing the flexible inner bag inside the squeezebottle. Such affixing usually involves heat sealing. The finish of the squeezebottle usually has a discharge opening smaller in circumference than the body of the squeezebottle so that the finish may later be capped with a reasonably sized closure. If the flexible inner bag is inserted into the squeezebottle from a small diameter discharge opening, it is difficult to insert a heat sealing tool into the flexible inner bag to seal the flexible inner bag to the upper half of the squeezebottle. A sealing tool would be expected to expand to press the flexible inner bag against the inner side wall of the squeezebottle. A reliable, high speed method for affixing a flexible inner bag to the inside of a squeezebottle, using an expanding tool, has been unavailable in many cases.
To avoid this problem packagers have resorted to a two-piece squeezebottle construction with an open bottom so that a flexible inner bag can be installed from a large opening in the bottom of the squeezebottle. After flexible inner bag installation, a bottom piece is sealed to the squeezebottle to close it. An example of this construction is disclosed in U.S. Pat. No. 4,842,165 to Van Coney. Van Coney's squeezebottle dispenser has a fluid-containing bag permanently sealed to the top and to the midpoint of the inside of a squeezebottle so that the fluid-containing bag inverts to dispense viscous fluid. The method securing the flexible inner bag to the squeezebottle is fusion welding, using a heated tool from inside the open bag. The bag is filled after sealing it to the container side wall. Closing the bag after filling may be another slow and difficult process.
For high speed filling and reduced part handling, it is most beneficial to have single-piece squeezebottles which can be filled from the discharge opening. Also, greater bottle shape flexibility is available with single-piece squeezebottles than with multiple piece constructions similar to Van Coney's. What is needed, however, is a bag-to-squeezebottle connection method which does not require the use of an expandable heated tool.
Others have used adhesives to affix bags inside containers. For example, U.S. Pat. No. 4,154,366 to Bonerb discloses an outer bag with an expandable liner having pressure-sensitive adhesive spots to secure the liner to the inside of the outer bag. The liner is inflated to expand it against the inside of the outer bag. The adhesive spots are on the top, sides, and bottom surfaces of the liner.
The problem with contact adhesives on a bag placed inside a squeezebottle is that they interfere with inserting and expanding the bag inside of the squeezebottle. When a flexible inner bag is inserted into the discharge opening of a single-piece squeezebottle, the bag has to be folded or partially collapsed to go through the opening. Then it has to be expanded inside the bottle before it can be bonded to the inside of the bottle.
Expansion may be hindered by contact adhesives bonding bag folds together. The expansion process also involves a certain amount of sliding between the flexible inner bag and the inner side wall of the squeezebottle, requiring a low coefficient of friction. Contact adhesives generally have a high coefficient of friction.
Induction sealing plastic parts together by heating metal embedded in one of the plastic parts, and by heating metal components which clamp the plastic parts together, are old in the art. Heat is developed by generating a high frequency oscillating magnetic field near the metal. Depending on the metal, either eddy current losses or magnetic hysteresis losses are believed responsible for heating the metal. Heat from the metal is then conducted through the plastic parts to their sealable interface. Plastic melting occurs from the conducted heat. If the plastic materials are compatible and sufficient pressure is applied, the plastic parts can be fusion welded together. The great benefit of the induction heating process is that heat can be quickly generated so that high production rates can be achieved.
Processes for sealing webs using induction sealing are old in the art. For example, U.S. Pat. No. 3,461,014 to James discloses a process in which ferrous oxide particles small enough to be mixed with conventional printing ink are printed onto a substrate. The substrate and web are combined and passed through a magnetic induction field to heat the ferrous oxide particles between the substrate and web. Then the web and substrate are passed through a pair of "squeeze rollers" to generate sufficient pressure to seal the webs together.